Solid or hollow fiber-reinforced resin members, which are formed by winding a strand of continuous filaments impregnated with a resin, increasingly attract attention because of their light weight and high strength For example, refer to JP, A, 63-166519, 63-166522 and 63-249628. In these publications, JP, A, 63-166519 discloses the use of a fiber-reinforced resin member for the piston rod of a hydraulic or pneumatic cylinder. However, there is a problem in that, when a fiber-reinforced resin member is used as a member such as the piston rod of a hydraulic or pneumatic cylinder, the spool of a hydraulic or pneumatic valve or the like, which is required to have an external surface having surface accuracy, it is difficult to secure the surface accuracy.
Namely, although JP, A, 63-166519 discloses the use of a fiber-reinforced resin member for the piston rod of a hydraulic or pneumatic cylinder, since the piston rod of the hydraulic or pneumatic cylinder hermetically slides in the cylinder, high surface accuracy is required for providing a seal between the rod and the sliding surface of the cylinder. In practice, it is therefore necessary to perform treatment for securing the surface accuracy of the external surface after a fiber-reinforced resin member rod has been produced in accordance with the proposal of JP, A, 63-166519 and then subjected to surface finish of the external surface by mechanical polishing. An example of such treatment is plating treatment for coating the external surface with a rigid material such as chromium or the like. This plating treatment is effected by a general method for plating the surfaces of conventional synthetic resins in accordance with the following procedure:
After the external surface of the fiber-reinforced resin member produced has been finished by mechanical polishing, a layer of a soft metal such as copper or the like is first formed on the external surface by plating, and a layer of a hard metal such as chromium or the like is then formed on the soft metal layer by plating.
However, since the fiber-reinforced resin member is made of a soft resin and a fiber material composed of continuous hard filaments, fine cracks occur in the soft resin portion when the external surface of the fiber-reinforced resin member is polished. When the external surface is plated to form the soft metal layer thereon, therefore, the plating solution used penetrates into the cracks. This causes insufficient coating of the soft metal layer and consequently the difficulty in coating of the hard metal layer with high strength. Further, since the soft resin portion is polished earlier than the hard fiber material, the hard fiber material remains raised on the surface, and it is thus difficult to finish the surface flatly. It is thus impossible to obtain high surface accuracy because, even if the external surface is subjected to plating suitable for the soft metal layer and the hard metal layer, unevenness remains on the surface of the hard metal layer in correspondence with the unevenness on the polished surface of the fiber-reinforced resin member.
It is an object of the present invention to provide a fiber-reinforced resin member which can attain high surface accuracy and a method of producing the resin member.